Donald Trump's rallies seem to have reached a tipping point, after the Republican frontrunner's announcement that he would be cancelling an event in Chicago saw the rally devolve into violence.Protesters and supporters came to blows as police worked to clear the room at the Chicago Pavilion. The event comes just three days before the state holds a pivotal winner-takes-all primary. Trump has several other events planned in Ohio in the coming days. Trump has repeatedly called for violence at his rallies and has publicly supported a heavy handed approach to dealing with the protesters who interrupt them.But early Saturday morning, Trump tweeted that the violence on display at his Chicago rally somehow demonstrated that "organized thugs" were "energizing people" in America.Trump's campaign seems to have crossed a threshold this week, after a North Carolina protester was sucker-punched in an incident that resulted in criminal charges for the attacker, and a chaotic rally in St. Louis was c